As a method of producing side seamless cans, a draw-ironing working has been known according to which a resin-coated metal plate obtained by coating a metal blank with an organic material is draw-ironed under dry conditions without using aqueous lubricant or coolant. However, if the resin-coated steel plate that uses a steel plate as a metal plate is subjected to the draw-ironing working, heat and iron powder are generated by the working often arousing a problem of defective forming. This method, therefore, is still not fully satisfactory from the standpoint of productivity. Besides, the defectively formed cans have a probability of developing corrosion occurring from the portions where the metal is exposed.
As a method of forming seamless cans, further, a stretch-draw forming has been placed in practical use to form seamless cans (patent document 1, etc.). According to this method, the resin-coated steel plate, too, can be formed under dry conditions without using aqueous lubricant, offering excellent productivity and environmental friendliness (patent document 1).
As a resin coating for a resin-coated steel plate used for the stretch-draw forming, there has, usually, been used a laminate of films of a polyethylene terephthalate or polyethylene terephthalate/isophthalate. For instance, there has been proposed a resin coating of a two-layer constitution comprising, as an upper layer, a polyethylene terephthalate/isophthalate containing 3 to 13 mol % of isophthalic acid and, as a lower layer, a polyethylene terephthalate/isophthalate containing 8 to 25 mol % of isophthalic acid (patent document 2).